linux-kernel - RE: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories support in spi-nor

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Message-ID: <BN7PR12MB2802C8279CA95FA08F8DDCF2DC8AA@BN7PR12MB2802.namprd12.prod.outlook.com>
Date:   Fri, 8 Dec 2023 17:06:24 +0000
From:   "Mahapatra, Amit Kumar" <amit.kumar-mahapatra@....com>
To:     Tudor Ambarus <tudor.ambarus@...aro.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "pratyush@...nel.org" <pratyush@...nel.org>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "richard@....at" <richard@....at>,
        "vigneshr@...com" <vigneshr@...com>,
        "sbinding@...nsource.cirrus.com" <sbinding@...nsource.cirrus.com>,
        "lee@...nel.org" <lee@...nel.org>,
        "james.schulman@...rus.com" <james.schulman@...rus.com>,
        "david.rhodes@...rus.com" <david.rhodes@...rus.com>,
        "rf@...nsource.cirrus.com" <rf@...nsource.cirrus.com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>
CC:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "michael@...le.cc" <michael@...le.cc>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
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        "claudiu.beznea@...on.dev" <claudiu.beznea@...on.dev>,
        "Simek, Michal" <michal.simek@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
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        "amitrkcian2002@...il.com" <amitrkcian2002@...il.com>
Subject: RE: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories support in
 spi-nor

Hello Tudor,

> -----Original Message-----
> From: Tudor Ambarus <tudor.ambarus@...aro.org>
> Sent: Wednesday, December 6, 2023 8:14 PM
> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@....com>;
> broonie@...nel.org; pratyush@...nel.org; miquel.raynal@...tlin.com;
> richard@....at; vigneshr@...com; sbinding@...nsource.cirrus.com;
> lee@...nel.org; james.schulman@...rus.com; david.rhodes@...rus.com;
> rf@...nsource.cirrus.com; perex@...ex.cz; tiwai@...e.com
> Cc: linux-spi@...r.kernel.org; linux-kernel@...r.kernel.org;
> michael@...le.cc; linux-mtd@...ts.infradead.org;
> nicolas.ferre@...rochip.com; alexandre.belloni@...tlin.com;
> claudiu.beznea@...on.dev; Simek, Michal <michal.simek@....com>; linux-
> arm-kernel@...ts.infradead.org; alsa-devel@...a-project.org;
> patches@...nsource.cirrus.com; linux-sound@...r.kernel.org; git (AMD-
> Xilinx) <git@....com>; amitrkcian2002@...il.com
> Subject: Re: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories support
> in spi-nor
> 
> 
> 
> On 12/6/23 14:30, Tudor Ambarus wrote:
> > Hi, Amit,
> >
> > On 11/25/23 09:21, Amit Kumar Mahapatra wrote:
> >> Each flash that is connected in stacked mode should have a separate
> >> parameter structure. So, the flash parameter member(*params) of the
> >> spi_nor structure is changed to an array (*params[2]). The array is
> >> used to store the parameters of each flash connected in stacked
> configuration.
> >>
> >> The current implementation assumes that a maximum of two flashes are
> >> connected in stacked mode and both the flashes are of same make but
> >> can differ in sizes. So, except the sizes all other flash parameters
> >> of both the flashes are identical.
> >
> > Do you plan to add support for different flashes in stacked mode? If
> > not, wouldn't it be simpler to have just an array of flash sizes
> > instead of duplicating the entire params struct?
> >
> >>
> >> SPI-NOR is not aware of the chip_select values, for any incoming
> >> request SPI-NOR will decide the flash index with the help of
> >> individual flash size and the configuration type (single/stacked).
> >> SPI-NOR will pass on the flash index information to the SPI core &
> >> SPI driver by setting the appropriate bit in
> >> nor->spimem->spi->cs_index_mask. For example, if nth bit of
> >> nor->spimem->spi->cs_index_mask is set then the driver would
> >> assert/de-assert spi->chip_slect[n].
> >>
> >> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-
> mahapatra@....com>
> >> ---
> >>  drivers/mtd/spi-nor/core.c  | 272 +++++++++++++++++++++++++++++-------
> >>  drivers/mtd/spi-nor/core.h  |   4 +
> >>  include/linux/mtd/spi-nor.h |  15 +-
> >>  3 files changed, 240 insertions(+), 51 deletions(-)
> >>
> >> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >> index 93ae69b7ff83..e990be7c7eb6 100644
> >> --- a/drivers/mtd/spi-nor/core.c
> >> +++ b/drivers/mtd/spi-nor/core.c
> >
> > cut
> >
> >> @@ -2905,7 +3007,10 @@ static void spi_nor_init_fixup_flags(struct
> >> spi_nor *nor)  static int spi_nor_late_init_params(struct spi_nor
> >> *nor)  {
> >>  	struct spi_nor_flash_parameter *params = spi_nor_get_params(nor,
> 0);
> >> -	int ret;
> >> +	struct device_node *np = spi_nor_get_flash_node(nor);
> >> +	u64 flash_size[SNOR_FLASH_CNT_MAX];
> >> +	u32 idx = 0;
> >> +	int rc, ret;
> >>
> >>  	if (nor->manufacturer && nor->manufacturer->fixups &&
> >>  	    nor->manufacturer->fixups->late_init) { @@ -2937,6 +3042,44 @@
> >> static int spi_nor_late_init_params(struct spi_nor *nor)
> >>  	if (params->n_banks > 1)
> >>  		params->bank_size = div64_u64(params->size, params-
> >n_banks);
> >>
> >> +	nor->num_flash = 0;
> >> +
> >> +	/*
> >> +	 * The flashes that are connected in stacked mode should be of same
> make.
> >> +	 * Except the flash size all other properties are identical for all the
> >> +	 * flashes connected in stacked mode.
> >> +	 * The flashes that are connected in parallel mode should be identical.
> >> +	 */
> >> +	while (idx < SNOR_FLASH_CNT_MAX) {
> >> +		rc = of_property_read_u64_index(np, "stacked-memories",
> idx,
> >> +&flash_size[idx]);
> 
> also, it's not clear to me why you read this property multiple times.
> Have you sent a device tree patch somewhere? It will help me understand
> what you're trying to achieve.

Miquel submitted the device tree patch; here is the series.
https://lore.kernel.org/all/20220126112608.955728-1-miquel.raynal@bootlin.com/

Regards,
Amit
> 
> >
> > This is a little late in my opinion, as we don't have any sanity check
> > on the flashes that are stacked on top of the first. We shall at least
> > read and compare the ID for all.
> >
> > Cheers,
> > ta